J1708 Port Duplication.

[nikitis]

So question.

I suspect the J1708 and J1939 networks operate like the older token ring networks that have to be terminated. When I was in college. Back in 2000 I setup a token ring networks for our dorm room and we basically invented LAN Parties. It was a couple years later Ethernet was a thing and networks didn't have to be terminated like with token rings, at least at the cable level.

I suspect our older buses work the same way because they require a resistor with any device you plug into it acting like the T Piece (Terminator) and they came from the same era so this is what they had to work with.

For those not in the know a token ring was essentially like a broadcast network where packets rounded the ring until it hit it's target hence the T Piece which would continue the loop or the "Ring" in token ring.

So I was thinking that if I wanted to add an additional J1708 port or two I could do so by simply tying into the two data wires, power, and ground wires twice and running them to two new J1708 ports. The devices like our "Bluefire" has the Terminator built into it, as does the AU device for J1708-J1939 translation when you buy it with the resistor but termination is built into both device which allows when plugged in to carry the broadcast signals of other devices.

I doubt anyone here has done this but maybe and if so I appeal to your experience, but if not, I'm thinking of trying this so I can have 3 J1708 ports. One open and available for diagnostics, one for Bluefire, and another for my AU device I may use here soon to upgrade my transmission and it will require one, at least the data lines.

I'm growing in my knowledge level and I'm at a stage where I'm starting to take on projects not many, if any, have gone and done.

Has anyone done this yet? And what are your thoughts?

 

[nikitis]

Guess it has been done already for 2 ports at least.

https://www.amazon.com/dp/B09X1RM4HR?tag=bravesoftwa04-20&linkCode=osi&th=1&psc=1&language=en_US

I guess I could buy two of them and plug them together to get 3 free ports.

So looking these closely they just T into the split so that should be all I need to do.

Gotta make a mount for three ports now. Will probably put them under my dash on the right side.

 

[tatersalad812]

If you split the wires off and make 3 plugs out of 1 it wont care one bit. Just make sure you are terminated if transmitting. Any device designed to go on a bus network should have a resistor built in. Ive also tested not having a resistor on my desk under a scope and while it seems to work on a short wire run id imagine a long run would cause problems. As long as you dont feed power into the canbus lines you really cant hurt much. Worst thing that happens is you have to cycle key to reset the bus. If you anger the bus enough it will just shut off till you cycle the key.

I was actually reading this when you replied lol

I would not recommend adding a bunch of splitters. I personally would solder in other plugs to the factory harness leaving my port available for a scan tool.

 

[cadillackid]

its a data BUS for a reason.. you can in fact parallel it out... thats how it works.. J1939 the same thing... each device on a J1708 (or 1939) has an address.. all the data goes to every device but only the device its addressed to cares and will use or respond back to the data stream

 

[nikitis]

its a data BUS for a reason.. you can in fact parallel it out... thats how it works.. J1939 the same thing... each device on a J1708 (or 1939) has an address.. all the data goes to every device but only the device its addressed to cares and will use or respond back to the data stream

Right but I think it's token ring tech even though nobody refers to it as that. Running RS232 protocols. I think they try to make it sound like it's this crazy complex proprietary network hardware but it's not.

Anyway, pic included for the Tri-Port Dash I'm thinking of doing.

 

[cadillackid]

It’s not token ring and it’s not rs232, it’s similar in nature to rs485, token ring literally before MAU existed each computer had to be active or the whole ring would go down. This is bus tech not ring tech . It’s not in one wire out the other .. it’s a tx/rx however you aren’t going through each device. Each device has a connection to the same tx/rx main lines kind of like a manifold ..

 

[nikitis]

It’s not token ring and it’s not rs232, it’s similar in nature to rs485, token ring literally before MAU existed each computer had to be active or the whole ring would go down. This is bus tech not ring tech . It’s not in one wire out the other .. it’s a tx/rx however you aren’t going through each device. Each device has a connection to the same tx/rx main lines kind of like a manifold ..

Each device didn't need to be active, but it did need to be terminated which was essentially a loopback. If that were the case enterprises of old using token networks would have required all PC's to be on. What did occur before Multistation Access Units (MAUs) is if several nodes were off and the distance between nodes was too far it would bring the remaining on PC's down. 382ft to be exact. As long as the NIC's of old had a T piece or end cap if it was at the end of the line, they'd work even off if within distance of the next node. They also came up with repeaters to help prevent that. If you had a PC at the end of a line that wasn't terminated all the PC's on that line would go down because the ring would be broken. It had to be a completed circuit (Ring in linear physical format). The "T" pieces were continuing the ring, and the End cap terminators were loopbacks to complete the circuits. Maximum length was 382ft between nodes. There were two types of token rings however. And also half-duplex vs full-duplex which made a token ring tokenless which changes things. I think J1708 mimics full-duplex because you can use unshielded twisted pair which is what is used and full duplex is for shorter distances.

You're right about it being the RS485 protocol. I got that one mixed up. I got mixed up thinking of rs232 cause the AU Device used that for the PC connection.

And I'm willing to bet it is similar token ring because the termination is done on PCB's of the devices you plug into it. The Docs also say the network uses twisted pair wiring like in token rings, and has to meet resistance standards. Too high of a resistance breaks it similarly to the token ring network.

 

[nikitis]

@Cadillackid

Is 12ga wire sufficient for the J1708? Or is it 10ga?

 

[tatersalad812]

@Cadillackid

Is 12ga wire sufficient for the J1708? Or is it 10ga?

I know you didnt ask me but here we are lol.

They dont carry any current you could use 22awg if you really wanted. I would use 14 or 16 to keep things nice and flexible. Just make sure you twist up the 2 signal wires

 

[nikitis]

I know you didnt ask me but here we are lol.

They dont carry any current you could use 22awg if you really wanted. I would use 14 or 16 to keep things nice and flexible. Just make sure you twist up the 2 signal wires

I've been reading up. Seems Cat5E or Cat6 for RS485 network just fine for industrial use. I've got over 1k feet of Cat 6 cable. I wired my whole house with ethernet years ago to up it's value so I'll use some of that. I may still get 12ga wire for the ground and Bat+ lines to match what's there currently as I'll be powering up 2-3 devices and I don't want the wire to be too thin it burns out, but the data lines with Cat6 should work fine.

I've been short Red and Black wire for awhile anyway. Time to order some.

 

[cadillackid]

I know you didnt ask me but here we are lol.

They dont carry any current you could use 22awg if you really wanted. I would use 14 or 16 to keep things nice and flexible. Just make sure you twist up the 2 signal wires

THIS!! theres no current pull on the wires.. you would only increase the gauge if you need to run it over a really far distance.. i used to work on RS485 based networks that spanned whole buildings and had sometimes multiple hundreds of feet between nodes.. (HVAC systems)..



navistar uses 14 gauge wire for most of their circuits.. although part of the J1708 diagnostics path in my redbyrd is 16 gauge.


running 12 or 10 gauge is really overkill and makes the wire more of a pain to install and terminate.. the pins for the Deutsch connectors def are not made to crimp in 10 gauge wire.. 12 mostly fits.. 14-16 seems to fit the pins best and still get a good crimp..

 

[cadillackid]

I've been reading up. Seems Cat5E or Cat6 for RS485 network just fine for industrial use. I've got over 1k feet of Cat 6 cable. I wired my whole house with ethernet years ago to up it's value so I'll use some of that. I may still get 12ga wire for the ground and Bat+ lines to match what's there currently as I'll be powering up 2-3 devices and I don't want the wire to be too thin it burns out, but the data lines with Cat6 should work fine.

I've been short Red and Black wire for awhile anyway. Time to order some.

cat5 / cat6 bulk cable is not designed to flex.. it is solid core wire.. using it in a vehicle where its subjected to flex isnt advised.. stranded cable such as that which is used to make patch cables is a better bet..



when we cabled large downtown tower buildings we had to leave LARGE service loops in various locations throughout riser rooms as big buildings move. quite a bit in heavy winds.. which would stretch and compress the network cabling causing issues.. the large service loops meant very minimal flex and of course MUCH LESS vibration than a vehicle would give the cable.

 

[tatersalad812]

I've been reading up. Seems Cat5E or Cat6 for RS485 network just fine for industrial use. I've got over 1k feet of Cat 6 cable. I wired my whole house with ethernet years ago to up it's value so I'll use some of that. I may still get 12ga wire for the ground and Bat+ lines to match what's there currently as I'll be powering up 2-3 devices and I don't want the wire to be too thin it burns out, but the data lines with Cat6 should work fine.

I've been short Red and Black wire for awhile anyway. Time to order some.

Just twist up some 14 or 16 in a drill and cut it to length that you need for your project.


If I can give you any advice, stay away from cheap wire, moisture loves to destroy the cheap stuff. 100% copper. Scamazon gets the new guys with alu clad wires and they rot after a few years from moisture in the air. If you solder that cheap stuff it seems like it dies faster. I use it around the house but never on a vehicle.... just some words of wisdom for anyone following.

 

[cadillackid]

Just twist up some 14 or 16 in a drill and cut it to length that you need for your project.


If I can give you any advice, stay away from cheap wire, moisture loves to destroy the cheap stuff. 100% copper. Scamazon gets the new guys with alu clad wires and they rot after a few years from moisture in the air. If you solder that cheap stuff it seems like it dies faster. I use it around the house but never on a vehicle.... just some words of wisdom for anyone following.

some of the stuff I find on fleabay or scama is aluminum thats been clad with copper, that stuff doesnt last well either...



really dont have to make a twisted pair with J1708 its only 9600 baud.. does look nicer to do it. however when working with J1939 / CAN. you definitely should make a twisted pair.. its at 250K or 500K depending on the vehicle... IH uses 250 up until maxxforce then they went 500

 

[tatersalad812]

True I forget its not required, I do it for aesthetics and so I know who the data wires are. I use black wire for everything so it all looks the same but can make finding the data wires in the wild a bit hard but if they are twisted you know exactly who they are... even if its a slight twist it makes it very obvious.

 

[nikitis]

My J1708 has 12 ga wire on it's port, so I'll use that for the battery and ground, then I'm just gonna use some thin ethernet cat6 or the data lines. It's shielded and coated so it'll be fine. I'll likely solder the cat6 into it to lengthen the distance to the ports.

I'm going to do 3 ports under dash on the right side. Going in this order:

[Grey 6 port , Green 9 port, Grey 6 port]

The green port is just using a J1708 lines only out of the 9 ports, it was a 6 port - 9 port adapter I'm going to slice up the grey end off and solder wires to it directly since my bluefire requires it.

I had a problem before where the wire from the first picture hung down hitting my legs. It wasn't ideal. This way the bluefire doesn't hang at all.

 

[tatersalad812]

My J1708 has 12 ga wire on it's port, so I'll use that for the battery and ground, then I'm just gonna use some thin ethernet cat6 or the data lines. It's shielded and coated so it'll be fine. I'll likely solder the cat6 into it to lengthen the distance to the ports.

I'm going to do 3 ports under dash on the right side. Going in this order:

[Grey 6 port , Green 9 port, Grey 6 port]

The green port is just using a J1708 lines only out of the 9 ports, it was a 6 port - 9 port adapter I'm going to slice up the grey end off and solder wires to it directly since my bluefire requires it.

I had a problem before where the wire from the first picture hung down hitting my legs. It wasn't ideal. This way the bluefire doesn't hang at all.

Id pick just about anything over cat anything cable, recycled wires from the bus anything but solid copper it work hardens!

 

[Dbacks2k4]

Guess it has been done already for 2 ports at least.

https://www.amazon.com/dp/B09X1RM4HR?tag=bravesoftwa04-20&linkCode=osi&th=1&psc=1&language=en_US

Oh cool, never knew such a thing existed. This will make going between my bluefire real time monitoring (on a tablet on my dash) over to my nexiq for actual diagnostics much easier!

Thanks!

 

[nikitis]

Oh cool, never knew such a thing existed. This will make going between my bluefire real time monitoring (on a tablet on my dash) over to my nexiq for actual diagnostics much easier!

Thanks!

And if you need 3 ports, buy two of them and daisy chain them lol!